A TV capable of displaying a stereoscopic video viewable with naked eye attracts attention. However, in such a TV, there is a case where stereoscopic effect cannot be obtained in some viewing positions, and in order to obtain a sufficient stereoscopic effect, a viewer has to move to the position where the stereoscopic effect is obtained. In particular, when a plurality of viewers exist, it is extremely annoying for each viewer to move to the position where the stereoscopic effect is obtained.
Accordingly, it is assumed to adjust a viewing area for obtaining the stereoscopic effect by TV. However, it is not easy to automatically adjust the viewing area by TV since the viewer does not always stay at the same position and the number of viewer is not always fixed.
Further, video data inputted into TV may include or not include parallax data or depth information necessary for reproducing a stereoscopic video. Thus, there is a fear that a viewing area automatically adjusted without considering the type of the video data is against the viewer's intention.
Furthermore, preference of the viewer is infinite in variety, and automatic adjustment ignoring the preference of the viewer is not desirable.